In-N-Out is the best. I was in SoCal a few weeks ago and made sure to grab a few.....even left hotel early to grab one more at LAX before flying out.

Whataburger is fine, just not In-N-Out good. They do have good shakes though.

I was very turned off of Five Guys by the service I got at one in HPN......though I suppose I would probably be turned off of any restaurant I would go to in HPN..